Thermally stable multilayer polymer extrusion

ABSTRACT

A combination of materials that may be formed through an extrusion process. The resulting product has at least two layers. By coextruding multiple layers of at least two types of materials together, the final product may have improved mechanical, thermal, electrical, and other properties as compared to the original materials used. Additionally, by using an additive, filler, or doping material in at least one layer of the final product during the extrusion process, the mechanical, thermal, electrical, or other properties of the final product may be further improved.

This application is a continuation of U.S. application Ser. No.16/831,898, filled Mar. 27, 2020, which claims the priority benefit ofU.S. Provisional Application No. 62/824,752, filed Mar. 27, 2019, eachof which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

Coextrusion is the process of forming an extrudate comprised of morethan one plastic melt stream. The process came about because someservice demands, particularly from the packaging industry, could not besatisfied by a single polymer although they could be met by acombination of polymers. Coextrusion was first practiced in theproduction of cast film and is now also used in blown film and sheetextrusion. The intention is normally to produce a laminar structure inwhich each layer contributes a key, property to the overall productperformance. Coextruded films may be very complex structures comprisedof many different functional layers, including tie layers whose purposeis to bond neighboring layers of limited compatibility.

Various components and materials have been used in the past formultilayer, coextrusion of polymeric materials. This process is able tocreate composite materials with properties that are not found in asingle material. Typically, a multilayer coextrusion process is employedto form sheets and film of polymeric materials having unique properties.Two or more diverse synthetic resinous materials may be simultaneouslyextruded from a single die opening to form a layered structure.

Besides being able to create very thin structures, coextrusion allows alarge amount of the layered material to be produced rapidly and costeffectively. Furthermore, multilayered structures with alternatingmechanical, electrical, or optical properties can enable a variety offunctional devices.

Additionally, the process of co-extrusion allows the addition ofadditives or fillers to the polymeric mixtures of one or multiplelayers. These fillers are added to polymers to accomplish many differentproperty changes and improvements. They can alter physical properties,reduce costs, trim weight, change the electrical conductivity, andenhance thermal properties, just to name a few. In almost every casethey also have an effect on processing behavior during extrusion.

There have been numerous compositions that have been manufactured in anattempt to modify the coefficient of thermal expansion of the resultantcomposition. In these compositions, structures contain networks of fiberreinforcing materials that serve to constrain movement as a function ofincreasing temperature. The difficulty in most of the previous materialsis that the processes used are a two-dimensional process that greatlylimits the potential geometry of the finished article.

In other cases, molded polymers having constrained coefficient ofthermal expansion properties have been produced using fibrousreinforcement. This method however is mostly impractical because moldingoperations require a flow pattern that results in orienting the fibersalong the flow patterns within the mold thereby creating a largecoefficient of thermal expansion wherein the finished part has a greatdifferential in coefficient of thermal expansion properties withinitself. Specifically, the coefficient of thermal expansion properties isreduced along the flow directions wherein the reinforcing fibers arealigned, but the coefficient of thermal expansion remains relativelylarge across the flow directions within the part.

Residential and commercial Window and door colors are getting darker byuser preferences. Consequently, the heat buildup on some of thecomponents on the exterior of the window and doors are getting upwardsof 230 degrees Fahrenheit. Traditionally, chlorinated polyvinyl chloridemay be a useful choice for some darker colors to maintain thermalstability because of the higher heat distortion temperature but as thewindow and door colors get to black and dark bronze, and designs arebecoming more flat, chlorinated polyvinyl chloride may still not bepreferable as it does not withstand the higher heats, for long periodsof time.

As another example, refrigerated tractor trailers have support beamsrunning through the length of the trailer that are currently made fromfoam polyvinyl chloride (PVC). The foam PVC may help to minimize cost.However, the part also needs a certain specific gravity (0.09 to 1.1) towithstand loads typically placed in a trailer.

SUMMARY OF THE INVENTION

An exemplary embodiment may address some or all of the shortcomings ofthe known art. An exemplary embodiment of the invention is a newcombination of materials that may be formed through an extrusionprocess. The resulting product has at least two layers. By coextrudingmultiple layers of at least two types of materials together, the finalproduct may have improved mechanical, thermal, electrical, and otherproperties as compared to the original materials used. Additionally, byusing an additive, filler, or doping material in at least one layer(e.g., multiple or all layers) of the final product during the extrusionprocess, the mechanical, thermal, electrical, or other properties of thefinal product may be further improved. However, in some other exemplaryembodiments, at least one layer may not comprise an additive, filler, ordoping material.

In at least one exemplary embodiment, at least one layer may comprisepolyvinyl chloride, high-density polyethylene, or other similar orsuitable material. The second layer may comprise a polycarbonate,acrylic, acrylonitrile styrene acrylate, acrylonitrile butadieneacrylate, chlorinated polyvinyl chloride, or other similar or suitablematerial. For example, the second layer may have at least one additionalfiller, additive, or doping material mixed in with the polymericmaterial. Some types of filler material include, but are not limited to,glass, talc, fibrous material, chemicals, metals, other mineral fillers,and other organic or inorganic materials. Other materials or materiallayers may be used if desired and compatible with at least one of theaforementioned layers.

The filler, additive or doping materials may be of any material that iscompatible with the material of the layer in which the filler is placed.Additionally, users may choose which filler, additive or dopingmaterials to use based on the properties that will be enhanced or addedto the final material. One or more filler material may be used.

In particular, it is desired that the fillers and materials selected beuseful in improving the thermal stability of the final product. Thermalstability is a substance's resistance to permanent property changescaused solely by heat. Decomposition temperature is a commonly usedmetric to assess thermal stability.

Additionally, the final material may have improved heat deflection,improved thermal movement, improved surface finish, or improved impactresistance. The final material may be able to provide better structuralstability, be produced at a lower cost and provide improved physical,electrical or other characteristics as needed.

In addition to the novel features and advantages mentioned above, otherbenefits will be readily apparent from the following descriptions of thedrawings and exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of one example of a final part that maybe achieved by a coextrusion process.

FIG. 2 is a side elevation view of a second example of a final part thatmay be achieved by a coextrusion process.

FIG. 3 is a side elevation view of a third example of a final part thatmay be achieved by a coextrusion process.

FIG. 4 is a side elevation view of a fourth example of a final part thatmay be achieved by a coextrusion process.

FIG. 5 is a side elevation view of a fifth example of a final part thatmay be achieved by a coextrusion process.

FIG. 6 is a side elevation view of a sixth example of a final part thatmay be achieved by a coextrusion process.

FIG. 7 is a side elevation view of a seventh example of a final partthat may be achieved by a coextrusion process.

FIG. 8 is a side elevation view of an eighth example of a final partthat may be achieved by a coextrusion process.

FIG. 9 is a side elevation view of a ninth example of a final part thatmay be achieved by a coextrusion process.

FIG. 10 is a side elevation view of a tenth example of a final part thatmay be achieved by a coextrusion process.

FIG. 11 is a side elevation view of an eleventh example of a final partthat may be achieved by a coextrusion process.

FIG. 12 is a side elevation view of a twelfth example of a final partthat may be achieved by a coextrusion process.

FIG. 13 is a side elevation view of a thirteenth example of a final partthat may be achieved by a coextrusion process.

FIG. 14 is a side elevation view of a fourteenth example of a final partthat may be achieved by a coextrusion process.

FIG. 15 is a side elevation view of a fifteenth example of a final partthat may be achieved by a coextrusion process.

FIG. 16 is a side elevation view of a sixteenth example of a final partthat may be achieved by a coextrusion process.

FIG. 17 is a side elevation view of a seventeenth example of a finalpart that may be achieved by a coextrusion process.

FIG. 18 is a side elevation view of an eighteenth example of a finalpart that may be achieved by a coextrusion process.

FIG. 19 is an exemplary chart of coefficient of linear thermal expansionand shrinkage for various embodiments of multilayer structurescomprising a PVC layer and a glass-filled polycarbonate layer.

FIG. 20 is an exemplary chart of shrinkage of polyvinyl chloride andchlorinated polyvinyl chloride.

FIG. 21 is an exemplary chart of shrinkage of examples of multilayerextrusions comprising a polyvinyl chloride layer and polycarbonatelayer.

FIG. 22 is an exemplary chart of shrinkage of examples of multilayerextrusions comprising a polyvinyl chloride layer and apolycarbonate—acrylonitrile butadiene styrene alloy composite.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

This disclosure describes exemplary embodiments of a composite part thatmay be made from a co-extrusion process, wherein the final part may haveimproved thermal stability. Additionally, depending on the materials andfillers used, the part may have improved mechanical, chemical,electrical or other properties. A combination of materials may be usedto achieve the desired properties. For example, a combination ofmaterials may be chosen to reduce cost, while increasing thermalstability and other properties and also giving the final part ahigh-quality appearance.

The final part may comprise at least two layers of different materials.At least one layer may be a polymeric material, wherein a filler,additive or doping material may be included in the polymeric material.The part may typically be made by a known coextrusion process. However,other suitable manufacturing processes may be employed.

Various combinations of materials may be chosen depending on theconditions the final part is required to withstand and the mechanical,thermal, chemical or other properties the final part is required tohave.

In an exemplary embodiment, the first layer may be a polymer,co-polymer, or other material having the desired characteristics. Thefirst layer may be any material that is chemically compatible with orotherwise connectable to (e.g. a tie layer may be used) the polymericmaterial of a second layer. In an exemplary embodiment, the material inthe first layer may be comprised of polyvinyl chloride (PVC),high-density polyethylene (HDPE), or other similar or suitable material.In another exemplary embodiment of a part having an overall thickness of0.040 to 0.060 inches, the first layer may be 0.001 inches to 0.050inches thick. More preferably, in such an embodiment, the first layermay be 0.005 inches to 0.030 inches thick and still more preferably thefirst layer may be 0.015 inches to 0.025 inches thick. In yet anotherexemplary embodiment having an overall thickness of 0.5 inches, thefirst layer may be 0.002 inches to 0.200 inches. Other exemplaryembodiments may have other overall thicknesses, as well as first layershaving other overall thicknesses, such as may be needed or beneficialfor particular parts or uses.

The second layer may be a polymer, co-polymer, or other material that ischemically compatible with or otherwise connectable to the first layer.Additionally, the material of the second layer may include a filler,additive or doping material to create a composite material. In anexemplary embodiment, the main component of the second layer maytypically be polycarbonate (PC), acrylic, acrylonitrile styrene acrylate(ASA), acrylonitrile butadiene acrylate (ABA), chlorinated polyvinylchloride (CPVC), or other similar or suitable material.

While some examples of materials are mentioned above for the differentlayers, many other types of the materials may be implemented in variousother embodiments. For example, standard plastics, engineering plastics,advanced engineering materials, and imidized materials may be used forany layer, which may be amorphous or crystalline materials, wherein thematerials of adjacent layers may or may not be compatible. For instance,in the event of incompatible layers, a tie layer may be used to bond theadjacent layers together. In the progression from standard plastics,engineering plastics, advanced engineering materials, to imidizedmaterials, the characteristics of the materials may generally transitionfrom being: 1) general purpose, lower stress tolerance, good bonding,and good formability; 2) engineering or structural grade and good wearresistance; to 3) higher temperature resistance, higher steamresistance, higher wear resistance, and higher chemical resistance.Examples of standard plastics include, but are not limited to,polystyrene (PS), acrylonitrile butadiene styrene (ABS), PVC,polypropylene (PP), HDPE, and low-density polyethylene (LDPE). Examplesof engineering plastics include, but are not limited to, polyphenyleneoxide (PPO), acrylic, PC, acetal, polyoxymethylene (POM), polyethyleneterephthalate (PTEP), ultra-high molecular weight polyethylene (UHMWPE), nylon, and polyamide (PA). Example of advance engineering materialsinclude, but are not limited to, polysulfone (PSU), polyphenylsulfone(PPSU), polyetherimide (PEI), polyphenylene sulfide (PPS),polyetheretherketone (PEEK), and Polytetrafluoroethylene (PTFE). Lastly,examples of imidized materials include, but are not limited to,polyimide (PI), polybenzimidazole (PBI), and polyamide-imide (PAI). Theparticular materials used for each layer of a multilayer structure maybe selected to achieve the desired physical characteristics. However,other factors may also factor into a selection of materials, such asmaterial availability, material costs, manufacturability, etc.

As stated above, the first or second layer (or additional layers inother embodiments) may contain a filler, additive, or doping materialthat is designed to improve the thermal, electrical, chemical or otherproperties of the final part. A user may select the appropriate filler,additive or doping material and the concentration of that material basedon the desired properties of the final part. The amount, and type, offiller added will depend on the physical or other properties that may begiven to the final part. In an exemplary embodiment, the filler may beadded in an amount from 10 wt. % to 45 wt. of the weight of the secondlayer, and more preferably the amount of filler added may be in theamount of between 30 wt. % and 40 wt. % of the weight of the secondlayer. In yet another exemplary embodiment, the filler may be added inan amount from 0 wt. % to 70 wt. % of the weight of the second layer,and more preferably the amount of filler added may be in the amount ofbetween 0.5 wt. % to 70 wt. % of the weight of the second layer. Otherexemplary embodiments may have other filler content, such as may beneeded or beneficial for particular parts or uses.

For example, a user may decide that the final part may need to haveincreased thermal stability. In this case, in addition to the thermalstability of the aforementioned polymer, a glass or fiber filler may beadded to the first or second layer to further increase the thermalstability of the final part. The filler may be added to the polymericmaterial during the compounding or extrusion process and may begenerally mixed into the polymer in a homogenous or non-homogenousmanner. Talc, chemicals, metals, other mineral fillers, or other organicor inorganic fillers may also be used to increase the thermal stability(or other physical properties) either alone or in conjunction with glassor fibrous filler.

In another embodiment, the second layer may be 0.001 inches to 0.030inches thick. More preferably, the second layer may be 0.008 inches to0.025 inches thick, and still more preferably the second layer may be0.012 inches to 0.018 inches thick. However, the thicknesses of thefirst and second layers may vary such as to account for the overallthickness of the product, the particular type of part or its uses, theparticular materials, or other considerations. For example, in anotherembodiment having an overall thickness of 0.500 inches, the first layermay have a thickness of 0.100 to 0.480 inches, and the second layer mayhave a thickness of 0.020 to 0.400 inches. Additionally, the secondlayer may be more preferably comprised of an acrylonitrile butadieneacrylate and chlorinated polyvinyl chloride copolymer with a fibrousglass filler.

In addition to thermal stability, other fillers may be used either aloneor in conjunction with other fillers to achieve other improvements inone or more properties. For example, if the final product needs improvedelectrical conductivity, aluminum powder, carbon fiber, or graphite maybe used. If the final product needs improved structural strength, boron,carbon, carbon fiber, Kevlar™ or other fibrous materials may be used.For improved resistance to combustion the addition of chlorine, bromine,phosphorous, or metallic salts may be useful. Other additives andproperties may be changed by the addition of other materials notmentioned herein, but generally known in the art.

Percentages of blends and combinations therein may vary from part topart as design requires (e.g., the amount of thermal stability or othermaterial property that is needed per the end application).

In one example, polyvinyl chloride may be used as the first layer.Acrylonitrile styrene acrylate, an acrylonitrile butadiene acrylate(e.g. ABS), or polycarbonate copolymer blend may be used as a secondlayer. The second layer may contain glass or other filler in ahomogenous mixture with the aforementioned polymer. In addition, a thirdlayer comprising polyvinyl chloride may be added to the other side ofthe second layer. In one exemplary embodiment of a product that has anoverall thickness of 0.060 inches, the first layer may be 0.001 inchesto 0.050 inches thick. More preferably, in this example, the first layermay be 0.005 inches to 0.030 inches thick and still more preferably thefirst layer may be 0.015 inches to 0.025 inches thick. Other exemplaryembodiments may have fewer or more layers, be comprised of differentmaterials, or have different thicknesses, such as to account for aparticular type of part or its uses, the particular materials, or otherconsiderations.

In the above example, the polyvinyl chloride may act to smooth out asurface and form a thin decorative cap. Other exemplary embodiments mayutilize other materials or layers to achieve a desirable surface (e.g.,an aesthetically pleasing or durable surface).

For instance, in another exemplary embodiment, the final part maycontain a fourth layer. In an exemplary embodiment of a product that hasan overall thickness of 0.060 inches, this fourth layer may be anultra-violet (UV) light protection layer. The UV protective layer may be0.001 inches to 0.010 inches thick. More preferably, the UV protectivelayer may be 0.003 inches to 0.008 inches thick and still morepreferably the UV protective layer may be 0.004 inches to 0.006 inchesthick. Again, other exemplary embodiments may have fewer or more layers,be comprised of different materials, or have different thicknesses, suchas to account for a particular type of part or its uses, the particularmaterials, or other considerations.

Turning now to the FIG. 1 , which shows a side view of at least one partthat may be formed by a coextrusion process. The part 5 a comprises afirst layer 10 a, a second layer 20 a, and a third layer 30 a. In thisexample, the first layer 10 a and third layer 30 a may be polyvinylchloride or high-density polyethylene. More specifically, the first andthird layers may be approximately 0.020 inches thick and may comprise aninterior grade rigid polyvinyl chloride. However, in this example, thirdlayer 30 a may also have portions 32 a, 34 a, and 36 a that haveincreased thickness (e.g., at respective corners of part 5 a that may besubject to more demands or forces when installed). The second layer 20 amay be a polymer or copolymer blend with a filler material to enhancethe chemical, electrical, mechanical or other physical properties of thefinal part. The second layer 20 a may also be a composite that iscoextruded with the first 10 a and third 30 a layers. An exemplaryembodiment of the part may also have an optional fourth layer 40 a thatis an ultra-violet coating designed to protect the part from degradationdue to exposure to light. In this example, the fourth layer 40 a extendsonly partially around the part 5 a, primarily around what may bereferred to as the outer or visible portion 7 a of part 5 a wheninstalled. More particularly, in this example, the fourth layer 40 aterminates at an end portion 42 a at or adjacent one corner of part 5 aand at an end portion 44 a at or adjacent another corner of part 5 a.Additionally, in this example, end portion 42 a interrupts and reducesthe thickness of portion 38 a of third layer 30 a, whereas end portion44 a gradually decreases in thickness as it terminates. Furthermore, inthis embodiment, the part may have attached additional elements orprojections 50 and 60 that are used to allow the part to be connected toor interact with other parts. In this exemplary embodiment, the attachedadditional elements or projections 50 and 60 may be a soft polyvinylchloride layer that serves as a seal or a friction fit into componentsthat the part is being connected to. Other exemplary embodiments mayutilize another soft or flexible material (e.g., an elastomer) forachieving a seal or a friction fit.

FIG. 2 shows a side view of an example of a second part 5 b. Thisembodiment may be similar to the first embodiment. The part 5 bcomprises a first layer 10 b, a second layer 20 b, and a third layer 30b. In this example, the first layer 10 b may be polyvinyl chloride orhigh-density polyurethane. The second layer 20 b may be a polymer orcopolymer blend with a filler material to enhance the chemical,electrical, mechanical or other physical properties of the final part.The second layer 20 b may also be extruded with the first 10 b and third30 b layers. An exemplary embodiment of the part may also have anoptional fourth layer 40 b that is an ultra-violet coating designed toprotect the part from degradation due to exposure to light. In thisexample, the fourth layer 40 b extends only partially around the part 5b, primarily around what may be referred to as the outer or visibleportion 7 b of part 5 b when installed. More particularly, in thisexample, the fourth layer 40 b terminates at an end portion 42 b at oradjacent one corner of part 5 b and at an end portion 44 b at oradjacent another corner of part 5 b. Additionally, in this example, endportion 42 b interrupts and reduces the thickness of portion 38 b ofthird layer 30 b, whereas end portion 44 b decreases in thickness as itterminates. Furthermore, in this embodiment, the part may have attachedadditional elements or projections 70, 80, and 90 that are used to allowthe part to be connected to or interact with other parts. In thisexemplary embodiment, the attached additional elements or projections70, 80, and 90 may be a soft polyvinyl chloride layer that serves as aseal or a friction fit into components to which the part is beingconnected or with which it is interacting. Again, other exemplaryembodiments may utilize another soft or flexible material (e.g., anelastomer) for achieving a seal or a friction fit.

FIG. 3 shows a side view of a third part 5 c that may be formed by thecoextrusion process. In this example, the part 5 c comprises an outerlayer 10 c, and an inner layer 20 c. The inner layer 20 c may be apolymer or copolymer blend with a filler material to enhance thechemical, electrical, mechanical or other physical properties of thefinal part. The inner layer 20 c may be coextruded with the outer layer10 c. In this embodiment, the part 5 c may have an additional element orprojection 95 that is used to allow the part to be connected to otherparts. In this embodiment, the attached additional element or projection95 may be a soft polyvinyl chloride layer that serves as a seal or afriction fit into components that the part is being connected to. Asbefore, other exemplary embodiments may utilize another soft or flexiblematerial (e.g., an elastomer) for achieving a seal or a friction fit.

FIG. 4 shows a side view of an example of another part 5 d that may beformed by a coextrusion process. In this example, the part 5 d comprisesa first layer 105, a second layer 110, and a third layer 115. In thisexample, the second layer 110 forms an inner surface 112 of part 5 d.The first layer 105 terminates and gradually decreases in thickness atan end portion 107 at or adjacent one end of part 5 d and at an endportion 109 at or adjacent an opposite end of part 5 d. Additionally, inthis example, the third layer 115 primarily forms an outer surface 116of part 5 d, which terminates and decreases in thickness at an endportion 117 at or adjacent one corner of part 5 d and at an end portion119 at or adjacent another corner of part 5 d. The first layer may becomprised of either polyvinyl chloride or high-density polyethylene. Thesecond layer 110 may be a polymer or copolymer blend with a fillermaterial to enhance the chemical, electrical, mechanical or otherphysical properties of the final part. The third layer 115 may be a UVcoating designed to protect the part from degradation due to exposure tolight. Other exemplary embodiments may implement other suitablematerials to protect against degradation due to light or weather.

FIGS. 5-11 show various examples of parts that may be comprised of afoamed polymer exterior and at least one glass filled polymer core.While these or other exemplary embodiments may refer to examples of theuse of glass filler, some examples of a core or other layer may notcomprise any fillers or may comprise different or additional fillers.FIG. 5 shows an example of a part 150 a in which a continuous glassfilled polymer core 160 a extends substantially through an entire lengthof a foamed polymer exterior 170 a. More particularly, the continuousglass filled polymer core 160 a extends substantially through an entirelength of part 150 a in this example. In addition, this embodiment ofglass filled polymer core 160 a may have opposing end portions 162 a and164 a that are each thicker than and extend substantially orthogonallyfrom a main portion 166 a. FIG. 6 shows a part 150 b that may be similarto part 150 a except for the absence of end portion 164 a.

On the other hand, FIG. 7 shows an example of a part 150 c that may besimilar to part 150 a except that that a main portion of the core layeris discontinuous. The localized segments may be useful for reinforcingor stabilizing particular areas of part 150 c. In particular, part 150 cis comprised of an L—shaped, glass filled polymer core segment 180 c andan L-shaped, glass filled polymer core segment 182 c, which arerespectively situated about corners 190 c and 192 c of part 150 c forenhanced stability and reinforcement.

FIG. 8 shows an example of a part 150 d that may be similar to part 150c except that a core bridge connects the L-shaped, glass filled polymersegments. In particular, part 150 d comprises a core bridge 184 d thatconnects the L-shaped, glass filled polymer segments. In this example,core bridge 184 d is of reduced thickness (i.e., localized wallreduction) than the adjacent portions 186 d and 188 d of the core layer.However, in other exemplary embodiments, a core bridge may haveincreased thickness relative to the adjacent portions of a core layer inorder to provide for increased stability or reinforcement through thatarea of the product.

FIG. 9 shows an example of a part 150 e that may be similar to part 150a except that a main portion of the core layer is discontinuous inmultiple places. In this example, part 150 e has a core in which a mainportion is divided into localized core segments 190 e, 192 e, and 194 e.For instance, the select placement of localized core segments may beuseful for a variety of reasons including, but not limited to, localizedstability or reinforcement, material availability or cost savings, thereception of mechanical hardware, etc.

FIG. 10 shows an example of a part 150 f that may be similar to part 150e except that the end portions of the core layer have been removed.Specifically, part 150 f has a core that is only comprised of localizedsegments 190 f, 192 f, and 194 f. While such segments are ofsubstantially equivalent size and are substantially equivalently spacedin FIG. 10 , other exemplary embodiments may have segments that are ofdifferent sizes or have different amounts of separation from an adjacentsegment. The size and placement of a segment may vary in differentembodiments for a variety of reasons including, but not limited to,localized stability or reinforcement, material availability or costsavings, the reception of mechanical hardware, etc.

In FIG. 11 , part 150 g may be similar to part 150 c of FIG. 7 . In thisexemplary embodiment, the localized, L-shaped core segments 180 g and182 g are of reduced size relative to the corresponding segments of FIG.7 . For example, the more localized (i.e., smaller) core segments ofFIG. 11 may be sufficient for a particular part or its uses.

FIGS. 12-18 show examples of another type of part, wherein any of theaforementioned considerations may also apply. The exemplary parts ofFIG. 12-18 may be comprised of a polymer substrate, at least one glassfilled polymer core, and a polymer capping layer that extends at leastpartially around the exterior of the part.

FIG. 12 shows an example of a part 200 a in which a continuous glassfilled polymer core 210 a extends substantially through an entire lengthof a polymer substrate 220 a. More particularly, the continuous glassfilled polymer core 210 a extends substantially through an entire lengthof part 200 a in this example. In addition, this embodiment of glassfilled polymer core 210 a may have opposing end portions 212 a and 214 athat extend substantially orthogonally from a main portion 216 a.Furthermore, in this example, a polymer capping layer 230 a extendspartially around the part 200 a, primarily around what may be referredto as the outer or visible portion 202 a of part 200 a when installed.More particularly, in this example, the polymer capping layer 230 aterminates at an end portion 232 a at or adjacent one corner 204 a ofpart 200 a and at an end portion 234 a at or adjacent another corner 206a of part 200 a. Additionally, in this example, the polymer cappinglayer 230 a interrupts and reduces the thickness of polymer substrate220 a as compared to the portion of polymer substrate 220 a that is notcovered by polymer capping layer 230 a. However, in other exemplaryembodiments, a polymer capping layer may not impact a thickness of anunderlying polymer substrate.

FIG. 13 shows a part 200 b that may be similar to part 200 a except forthe absence of end portion 214 a.

On the other hand, FIG. 14 shows an example of a part 200 c that may besimilar to part 200 a except that that a main portion of the core layeris discontinuous. The localized segments may be useful for reinforcingor stabilizing particular areas of part 200 c. In particular, part 200 cis comprised of an L—shaped, glass filled polymer core segment 240 c andan L-shaped, glass filled polymer core segment 242 c, which arerespectively situated about corners 250 c and 252 c of part 200 c forenhanced stability and reinforcement.

FIG. 15 shows an example of a part 200 d that may be similar to part 200c except that a core bridge connects the L-shaped, glass filled polymersegments. In particular, part 200 d comprises a core bridge 244 d thatconnects the L-shaped, glass filled polymer segments. In this example,core bridge 244 d is of reduced thickness (i.e., localized wallreduction) than the adjacent portions 246 d and 247 d of the core layer.However, in other exemplary embodiments, a core bridge may haveincreased thickness relative to the adjacent portions of a core layer inorder to provide for increased stability or reinforcement through thatarea of the product. Additionally, in this example, portion 246 d has anotched corner 248 d, and portion 247 d has a notched corner 249 d,wherein a notched corner or other area of reduced thickness may beuseful for various reasons including, but not limited to, increasedflexibility in that area, reduced need for localized stability orreinforcement in that area, material availability considerations,material cost considerations, etc.

FIG. 16 shows an example of a part 200 e that may be similar to part 200a except that a main portion of the core layer is discontinuous inmultiple places. In this example, part 200 e has a core in which a mainportion is divided into localized core segments 250 e, 252 e, and 254 e.For instance, the select placement of localized core segments may beuseful for a variety of reasons including, but not limited to, localizedstability or reinforcement, material availability or cost savings, thereception of mechanical hardware, etc.

FIG. 17 shows an example of a part 200 f that has a core that is onlycomprised of localized segments 250 f, 252 f, and 254 f. While suchsegments are of similar size and are substantially equivalently spacedin FIG. 17 , other exemplary embodiments may have segments that are ofdifferent sizes or have different amounts of separation from an adjacentsegment. The size and placement of a segment may vary in differentembodiments for a variety of reasons including, but not limited to,localized stability or reinforcement, material availability or costsavings, the reception of mechanical hardware, etc.

In FIG. 18 , part 200 g may be similar to part 200 c of FIG. 14 . Inthis exemplary embodiment, the localized, L-shaped core segments 240 gand 242 g are of reduced size relative to the corresponding segments ofFIG. 14 . For example, the more localized (i.e., smaller) core segmentsof FIG. 18 may be sufficient for a particular part or its uses.Regarding the aforementioned examples, other exemplary embodiments mayutilize other suitable materials, layers, thicknesses, and terminationpoints (if any) such as may be needed or beneficial for a particularpart or its uses, physical properties, material availability, costconsiderations, or other factors. Such as addressed above, it should benoted that these material combinations may not always be homogeneously,continuously, or consistently blended or provided throughout the part.For example, while a homogenous blend may be used for the thermallystable layer, a layer may be distinct from other layers that may serveas legs, connectors, or capstocks in the final part. Furthermore, one ormore thermally stable layers may be co-extruded within the final part tocreate more thermally stable areas of a final part, or a completelythermally stable part up to the temperatures the thermally stable partis designed to perform best under.

FIG. 19 is a chart of coefficient of linear thermal expansion (CLTE) andshrinkage for examples of multilayer core extrusions (MCE) comprised ofvarious materials. In particular, each example comprised an outer coreof PVC and an inner core of a glass filled polycarbonate (PC) composite.The chart provides examples of how CLTE and shrinkage may be improved bychanges in the thicknesses of the layers and/or in the content of theinner core material. Although not addressed in this example, changes inthe outer core material would also impact CLTE and shrinkage.

The charts of FIGS. 20-22 address shrinkage of other examples ofstructures. FIG. 20 first compares shrinkage of only a PVC layer or aCPVC layer at different temperatures. FIG. 21 addresses shrinkage ofmultilayer core extrusions comprising a PVC layer and a PC layer atdifferent amounts of filler content in the PC layer, differenttemperatures, and different layer thicknesses. For further comparison,FIG. 22 considers similar factors that affect shrinkage of multilayercore extrusions comprising a PVC layer and a PC-ABS alloy composite.Again, among other factors, filler content, layer thicknesses, andtemperature variations may be varied to individually or collectivelyimpact the physical characteristics (e.g., shrinkage or CLTE) of acomponent.

In one exemplary embodiment, the final product may be used as a glazingfor windows or doors. In this embodiment, the second layer may comprisean approximately 0.015 inches thick glass filled ABS or polycarbonatecomposite. Additionally, this embodiment may have a first layer that maybe an approximately 0.040 inches thick layer of PVC. This combinationhas the potential to generate an improved thermal stability, improvedimpact resistance, and improved appearance while simultaneouslydecreasing the cost of the part. Achieving these results is not possiblewith a pure PVC or CPVC part.

In another embodiment, support structures may be made stronger by addingan internal layer that is made out of a glass filled material (e.g. aglass filled PVC composite). By using a glass filled PVC composite, thefinal parts used in the support structure may be produced with aspecific gravity as low as 0.5, thereby reducing the weight of thetrailer, while still meeting structural requirements.

While the product presented herein has been described with reference tovarious embodiments, those skilled in the art will understand thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope and essence of thedisclosure. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the disclosurewithout departing from the essential scope thereof. Therefore, it isintended that the product presented herein not be limited to theparticular embodiments disclosed. Also, all citations referred to hereinare expressly incorporated herein by reference.

What is claimed is:
 1. A method for forming a multilayer structure, saidmethod comprising: coextruding a first layer comprising polyvinylchloride with a second layer comprising a polycarbonate orpolycarbonate/ABS blend composite that includes glass filler; whereinsaid second layer is formed on at least one side of said first layer;wherein said multilayer structure has improved thermal stability ascompared to a similar structure except without said second layer; andwherein said improved thermal stability is adapted to result in a higherheat deflection temperature, a lower coefficient of linear thermalexpansion, and decreased shrinkage.
 2. The method of claim 1 whereinsaid polycarbonate or polycarbonate/ABS blend composite of said secondlayer comprises an additional filler, additive, or doping material,which is selected to improve physical, chemical, or electricalproperties of said multilayer structure.
 3. The method of claim 2wherein: said additional filler, additive, or doping material isselected from the group consisting of talc, fibrous material, chemicals,metals, other mineral fillers, or combinations thereof.
 4. The method ofclaim 2 wherein said additional filler, additive, or doping material isadapted to improve electrical conductivity of said multilayer structure.5. The method of claim 4 wherein said additional filler, additive, ordoping material is selected from the group consisting of aluminumpowder, carbon fiber, and graphite.
 6. The method of claim 2 whereinsaid additional filler, additive, or doping material is adapted toimprove structural strength of said multilayer structure.
 7. The methodof claim 6 wherein said additional filler, additive, or doping materialis selected from the group consisting of Kevlar™, carbon, boron, carbonfiber, and combinations thereof.
 8. The method of claim 1 furthercomprising: coextruding a third layer with said first layer and saidsecond layer; wherein said third layer is on a second side of saidsecond layer opposite said first layer; and wherein said third layercomprises polyvinyl chloride.
 9. The method of claim 8 furthercomprising: coextruding a fourth layer with said first layer, saidsecond layer, and said third layer; wherein said fourth layer is anultraviolet protection layer.
 10. The method of claim 1 furthercomprising: coextruding a third layer with said first layer and saidsecond layer; wherein said third layer is an ultraviolet protectionlayer.
 11. The method of claim 1 wherein: at least one of said firstlayer and said second layer has an additional filler, additive, ordoping material; and said additional filler, additive, or dopingmaterial is selected to improve physical, chemical, or electricalproperties of said multilayer structure.
 12. The method of claim 1wherein said second layer is separated into multiple localized segments.13. The method of claim 1 wherein said polyvinyl chloride of said firstlayer is foamed polyvinyl chloride.
 14. The method of claim 1 whereinsaid first layer comprises a filler, additive, or doping material, whichis selected to improve thermal stability of said multilayer structure.15. The method of claim 1 wherein said first layer comprises a filler,additive, or doping material, which is selected to improve physical,chemical, or electrical properties of said multilayer structure.
 16. Themethod of claim 15 wherein: said filler, additive, or doping material isselected from the group consisting of talc, fibrous material, chemicals,metals, other mineral fillers, or combinations thereof.
 17. The methodof claim 15 wherein said filler, additive, or doping material is adaptedto improve electrical conductivity of said multilayer structure.
 18. Themethod of claim 17 wherein said filler, additive, or doping material isselected from the group consisting of aluminum powder, carbon fiber, andgraphite.
 19. The method of claim 15 wherein said filler, additive, ordoping material is adapted to improve structural strength of saidmultilayer structure.
 20. The method of claim 19 wherein said filler,additive, or doping material is selected from the group consisting ofKevlar™, carbon, boron, carbon fiber, and combinations thereof.